1. Field of the Invention
The present invention relates to semiconductor manufacturing process technologies, in particular, to an overhead hoist transport system.
2. Description of the Prior Art
In the manufacturing process for forming a semiconductor device, the wafer is an important substrate material. In order to decrease the possibility of the waters being damaged when the wafers are transported, the overhead hoist transport (OHT) system is usually to be used for transporting the wafers. The overhead hoist transport system is not only smooth, but also the transportation time can be precisely controlled, thereby enhancing the stability of the wafer transporting effectively.
However, the conventional overhead hoist transport system mainly comprises a rail and a stocker with wheels, and the stocker is moving along the rail through the wheels. Since the wheels directly contact the rail, some particles and dust will be formed during the rubbing between the wheels and the rail, and these particles most likely to drop down on the top surface of the stocker. If the positioning sensor chip is covered by these particles, the position system of the stocker will be affected, may even increase the possibility of the overhead hoist transport system shut down, and this will require more labor to be spent to correct the overhead hoist transport system malfunction.
Therefore, the applicant provides an overhead hoist transport system, which can effectively reduce the shutting down possibility of overhead hoist transport systems occurring when particles drop down.